add rounding-using-doubles methods on SkScalar and SkRect

include/core/SkRect.h

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef SkRect_DEFINED
@@ skipping 714 matching lines @@
      *  Set the dst rectangle by rounding this rectangle's coordinates to their
      *  nearest integer values using SkScalarRoundToInt.
      */
     void round(SkIRect* dst) const {
         SkASSERT(dst);
         dst->set(SkScalarRoundToInt(fLeft), SkScalarRoundToInt(fTop),
                  SkScalarRoundToInt(fRight), SkScalarRoundToInt(fBottom));
     }
 
     /**
+     *  Variant of round() that explicitly performs the rounding step (i.e. floor(x + 0.5)) using
+     *  double instead of SkScalar (float). It does this by calling SkDScalarRoundToInt(), which
+     *  may be slower than calling SkScalarRountToInt(), but gives slightly more accurate results.
+     *
+     *  e.g.
+     *      SkScalar x = 0.49999997f;
+     *      int ix = SkScalarRoundToInt(x);
+     *      SkASSERT(0 == ix);  // <--- fails
+     *      ix = SkDScalarRoundToInt(x);
+     *      SkASSERT(0 == ix);  // <--- succeeds
+     */
+    void dround(SkIRect* dst) const {
+        SkASSERT(dst);
+        dst->set(SkDScalarRoundToInt(fLeft), SkDScalarRoundToInt(fTop),
+                 SkDScalarRoundToInt(fRight), SkDScalarRoundToInt(fBottom));
+    }
+
+    /**
      *  Set the dst rectangle by rounding "out" this rectangle, choosing the
      *  SkScalarFloor of top and left, and the SkScalarCeil of right and bottom.
      */
     void roundOut(SkIRect* dst) const {
         SkASSERT(dst);
         dst->set(SkScalarFloorToInt(fLeft), SkScalarFloorToInt(fTop),
                  SkScalarCeilToInt(fRight), SkScalarCeilToInt(fBottom));
     }
 
     /**
@@ skipping 38 matching lines @@
      */
     void sort();
 
     /**
      *  cast-safe way to treat the rect as an array of (4) SkScalars.
      */
     const SkScalar* asScalars() const { return &fLeft; }
 };
 
 #endif